Laser marking of polymer substrates is known. In some articles, a single layer in a multilayered substrate is marked by passing laser light through one or more layers that are “transparent” to the wavelength(s) of light generated by the laser. The substrate layer sensitive to the laser may simply char upon contact with the wavelength(s) of light emitted by the laser. In some instances, the markable layer can comprise a laser-sensitive pigment, dye or the like. However, the aforementioned “transparent” layers can still be damaged or modified in some way when exposed to the energy of the laser. Mild damage is often of no serious consequence where the transparent layer is merely decorative or serves a protective function for one or more underlying layers.
The exposure of multilayered substrates to laser light is more problematic where specific layers of materials possess performance properties important to the finished product, and the art has sought to avoid exposing such materials to laser light during the marking of another layer in the article. Layers of adhesive(s), release agent(s), or the like are exemplary of the functional materials which are not normally exposed to laser irradiation during such a marking process.
Additionally, traditional printing methods have not been satisfactory when used on layered materials that include, for example, a release agent. The application of a printed image to the surface of a layer of release agent is typically complicated by poor wetting and/or poor adhesion and can adversely impact the ability of the release agent to adhere to or to release from a pressure sensitive adhesive. Moreover, printing onto a surface prior to the application of a release agent can add steps to the manufacturing process and can adversely impact the ability of the release agent to adhere to the printed surface.